cursor.max()
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Definition
cursor.max()
Important
mongosh Method
This page documents a
mongosh
method. This is not the documentation for a language-specific driver, such as Node.js.For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.
Specifies the exclusive upper bound for a specific index in order to constrain the results of
find()
.max()
provides a way to specify an upper bound on compound key indexes.
Parameters
The max()
method has the following parameter:
Parameter | Type | Description |
---|---|---|
indexBounds | document | The exclusive upper bound for the index keys. |
The indexBounds
parameter has the following prototype form:
{ field1: <max value>, field2: <max value2> ... fieldN:<max valueN> }
The fields correspond to all the keys of a particular index in order.
Note
Index Use
max()
exists primarily to support the
mongos
(sharding) process.
Compatibility
This method is available in deployments hosted in the following environments:
MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud
Note
This command is supported in all MongoDB Atlas clusters. For information on Atlas support for all commands, see Unsupported Commands.
MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB
Behavior
Interaction with Index Selection
Because max()
requires an index on a field,
and forces the query to use this index, you may prefer the
$lt
operator for the query if possible. Consider the
following example:
db.products.find( { _id: { $in: [ 6, 7 ] } } ).max( { price: NumberDecimal("1.39") } ).hint( { price: 1 } )
The query will use the index on the price
field, even if
the index on _id
may be better.
Index Bounds
max()
without min()
The min()
and max()
methods
indicate that the system should avoid normal query planning. They
construct an index scan where the index bounds are explicitly specified
by the values given in min()
and
max()
.
Warning
If one of the two boundaries is not specified, the query plan will be an index scan that is unbounded on one side. This may degrade performance compared to a query containing neither operator, or one that uses both operators to more tightly constrain the index scan.
Example
Note
For the examples below, create a sample collection named products
that holds the
following documents:
db.products.insertMany([ { "_id" : 1, "item" : "apple", "type" : "honey crisp", "price" : NumberDecimal("1.99") }, { "_id" : 2, "item" : "apple", "type" : "fuji", "price" : NumberDecimal("1.99") }, { "_id" : 3, "item" : "apple", "type" : "jonagold", "price" : NumberDecimal("1.29") }, { "_id" : 4, "item" : "apple", "type" : "jonathan", "price" : NumberDecimal("1.29") }, { "_id" : 5, "item" : "apple", "type" : "mcintosh", "price" : NumberDecimal("1.29") }, { "_id" : 6, "item" : "apple", "type" : "cortland", "price" : NumberDecimal("1.29") }, { "_id" : 7, "item" : "orange", "type" : "cara cara", "price" : NumberDecimal("2.99") }, { "_id" : 9, "item" : "orange", "type" : "satsuma", "price" : NumberDecimal("1.99") }, { "_id" : 8, "item" : "orange", "type" : "valencia", "price" : NumberDecimal("0.99") }, { "_id" : 10, "item" : "orange", "type" : "navel", "price" : NumberDecimal("1.39") } ])
Create the following indexes for the collection:
db.products.createIndexes( [ { "item" : 1, "type" : 1 }, { "item" : 1, "type" : -1 }, { "price" : 1 } ] )
Using the ordering of
{ item: 1, type: 1 }
index,max()
limits the query to the documents that are below the bound ofitem
equal toapple
andtype
equal tojonagold
:db.products.find().max( { item: 'apple', type: 'jonagold' } ).hint( { item: 1, type: 1 } ) The query returns the following documents:
{ "_id" : 6, "item" : "apple", "type" : "cortland", "price" : NumberDecimal("1.29") } { "_id" : 2, "item" : "apple", "type" : "fuji", "price" : NumberDecimal("1.99") } { "_id" : 1, "item" : "apple", "type" : "honey crisp", "price" : NumberDecimal("1.99") } Using the ordering of the index
{ price: 1 }
,max()
limits the query to the documents that are below the index key bound ofprice
equal toNumberDecimal("1.99")
andmin()
limits the query to the documents that are at or above the index key bound ofprice
equal toNumberDecimal("1.39")
:db.products.find().min( { price: NumberDecimal("1.39") } ).max( { price: NumberDecimal("1.99") } ).hint( { price: 1 } ) The query returns the following documents:
{ "_id" : 10, "item" : "orange", "type" : "navel", "price" : NumberDecimal("1.39") }